The Effect Of Gravity On Space-time

Hi. I am a layman, not a physicist, however I am always fascinated by visualizations of how the universe works. For example, last night I was watching a program which portrayed how objects interact with space-time and what effect that object's gravity would have on time.

I am not well versed in physical laws but I do like to try and make sense of these things. As such, I would like to share some thoughts:

Objects of mass are objects of gravity. They sit in space-time and their gravity warps space-time around them. The more massive they are, the stronger the force of gravity they possess, and the slower time moves within the influence of it's gravitational field. We also know that the faster an object travels, the less it is affected by time (or maybe it's just that, as with gravity, time moves more slowly).

Gravity affects time because mass distorts space-time. As an object travels faster, it's mass increases, and as such it's gravitational force must also increase, and so an object of lesser mass can have the same affect on time as and object with great mass if it is traveling fast enough. With all that in mind:

1: Could an object with low mass traveling fast enough through space become a black hole?

2: if the above is true, would that be the ultimate barrier to exceeding faster than light travel in normal space (assuming one could surpass the other barriers)?

3: Does all of this imply that a body in motion will have less of an effect on space-time than an object with the same mass that is in motion?

I would appreciate it if someone could point out the flaws in my line of reasoning in as simple a manner as possible. As stated, I am a layman.

No. Mass is an invariant.

Its not.

No.

Yeah, your first premise is wrong.

Almost, but it is the acceleration, not the speed. This is called the equivalence principle.

http://en.wikipedia.org/wiki/Equivalence_principle

Basically, it's like the extra weight you sense when an elevator starts to move. As the elevator accelerates up to its normal speed you feel a bit heavier, but once it reaches its constant speed you no longer feel any different than you do under Earth's normal gravity. With a great enough constant acceleration you could feel the same as Earth's gravity, even though you are not near enough mass to produce it.

No, this has to do with your frame of reference.

http://en.wikipedia.org/wiki/Inertial_frame_of_reference

At any constant speed, even close to that of light, you wouldn't notice any change of mass in anything moving with you. Now someone moving at a different speed or direction may very well observe you to have a greater mass, due to momentum. This is due to the relativity of simultaneity.

http://en.wikipedia.org/wiki/Relativity_of_simultaneity

Basically, depending on how an observer is moving relative to you, they may observed your speed to be faster or slower than you do.

Once again, any change in gravity you feel would be due to acceleration.

Thank you for your reply. I will check those links and try to wrap my head around the information I find.

I do have a couple of questions:

If you were to reach that level of acceleration, would you actually affect objects around you (assuming they were not travelling with you) as if you possessed the Earth's gravitional force?

Is it true that an object moving towards the speed of light (or at the speed of light, or something to that effect) becomes infinitely massive? Or am I mixing up what little I do know? I understand what you are saying about it being relative, but what about the affect such an object would have on space-time. It permeates everything, so relatively we are always moving through it and affecting it. As such, would two equally massive objects moving at different speeds affect space-time in different magnitudes?

I apologize if I have missed the point. I will read the links you provided and look for answers there, as well.

No, mass is an invariant. It would appear to you as if the high speed object just passed you gravitationally affected only by what little mass you have.

No. The momentum is
p = mdx/dτ
where the mass m is an invariant which is something that does NOT change with speed.
Transforming the time to your lab's time due to time dilation you get
p = γmdx/dt
As a gimmick it has become popular to couple the γ with the m from which it didn't actually come and define a new kind of mass
M=γm
but it isn't actually meaningful to do that. The real mass is m and it didn't change with speed.

That is one thing I have not understood yet, you say mass is invariant yet I was lead to believe that the mass of a object increases when speed goes up to closer to the speed of light.
How can the two be understood?

SS,

Here's a very good link that explains your original question.

http://www.weburbia.com/physics/black_fast.html

No, the force you feel as gravity when accelerated is completely dependent on your frame. IOW, the acceleration is direction dependent, so it only adds a sense of gravity to co-moving objects.

No, its kinetic energy increases without bounds. The mass-energy equivalence is only applicable to invariant mass. Within such a frame this energy is always attributed to another frame. IOW, you'd always observe your frame to be at rest and others to be the ones moving.

http://en.wikipedia.org/wiki/Principle_of_relativity

This applies to any frame with a constant velocity.

No problem. These are difficult concepts to get a handle on, and probably will not become clear without some significant study. This is another good reference:

http://en.wikipedia.org/wiki/Mass%E2%80%93...tems_of_objects

This post has been edited by synthsin75 on Dec 23 2011, 07:12 PM

It's the difference between rest mass and relativistic mass, explained here:

http://en.wikipedia.org/wiki/Mass%E2%80%93...tems_of_objects

Thank you for the helpful responses. It makes my head swim a little, but that's the attraction of it.

So if we accelerate an object to near the speed of light so that it will catch up with a galaxy that is receding just that little slower (so it can catch up with it). When they met the probe slows a little but lands on some exoplanet. It is still moving away from us at a relativistic speed.

The Galaxians weight the object.

a . Will it still have part of it relativistic mass?

B. Weigh the same as what it was on Earth when it started off (Rest mass)?

B, because they'd have to slow it down to their speed to weight it. The probe always has rest mass in it's own frame, and when it's frame is made co-moving with that of the measuring observer, it still has only its rest mass, as its own frame is now equal to that of the observer.

Well that is where I would have chosen a. It will have retained some of its relativistic mass as it is still moving near light speed away from us, the point where it originated.

So you went B (well it seems like you did) but I went A. Any other takers?

Science isn't a poll.

I want your answers and reasons really, the poll was just a choice, maybe you can have C. Something other than the above as 3rd choice.

There is no weight gain. There is no change in mass. Its a gimmick.
The relativistic law of motion where F and A are four-vectors is
F=mA
where m is an invariant. It does NOT change with speed. Its not a mass Vs rest mass thing, its the exact same value regardless of speed. Coupling the time dilation coefficient with the mass so that the momentum equation can be rewritten as
p = Mdx/dt
is nothing more than a meaningless gimmick that does nothing better than to confuse people like you into thinking there is some kind of speed dependent weight change or that the mass is somehow different at rest and him into thinking speed will essentially collapse things into black holes.
Just leave the time dilation associated with the time from which it came and define mass as the invariant associated with the length of the momentum 4-vector and suddenly all that confusion goes away and you no longer have to write a million zero subscripts all over in your equations.